class_docstr: Some trading strategy make decisions based on other prediction signals
  The signals may comes from different sources(e.g. prepared data, online prediction from model and dataset)
  
  This interface is tries to provide unified interface for those different sources
class_docstr_tok: ["Some","trading","strategy","make","decisions","based","on","other","prediction","signals","The","signals","may","comes","from","different","sources","(","e.g",".","prepared","data",",","online","prediction","from","model","and","dataset",")","This","interface","is","tries","to","provide","unified","interface","for","those","different","sources"]
docstr: get the signal at the end of the decision step(from `start_time` to `end_time`)
  
  Returns
  -------
  Union[pd.Series, pd.DataFrame, None]:
      returns None if no signal in the specific day
docstr_tok: ["get","the","signal","at","the","end","of","the","decision","step","(","from","`","start_time","`","to","`","end_time","`",")","Returns","--","--","--","-","Union","[","pd.Series",",","pd.DataFrame",",","None","]",":","returns","None","if","no","signal","in","the","specific","day"]
code: def get_signal(
      self, start_time: pd.Timestamp, end_time: pd.Timestamp
  ) -> Union[pd.Series, pd.DataFrame, None]:
      """
      get the signal at the end of the decision step(from `start_time` to `end_time`)
  
      Returns
      -------
      Union[pd.Series, pd.DataFrame, None]:
          returns None if no signal in the specific day
      """
  
file_path: qlib/qlib/backtest/signal.py
imports: import abc
  from typing import Dict, List, Text, Tuple, Union
  import pandas
  from qlib.utils import init_instance_by_config
  from ..data.dataset import Dataset
  from ..data.dataset.utils import convert_index_format
  from ..model.base import BaseModel
  from ..utils.resam import resam_ts_data
label_desc: Use image node_id 1 for calling the Signal obj's underlying member method code with example usage: obj.get_signal(start_time, end_time) without return types